What are these "things"?

NZ Wood Pigeon dropping perchance?

My wife has been collecting leaves and other autumnal matter for pre-school for their nature table, leaf rubbings and the like.  Whilst looking for suitable stuff and I came across these "things".  Looking at the second shot, the fact that this collection was underneath a tree and that I'd seen a wood pigeon in the vicinity a little earlier, makes me think perhaps these are seeds from some fruit the bird had been eating ... but which plant is the seed from, if indeed that's what they are?

Don't worry, none of these things have gone to pre-school!!

So, can you help?  Do you know what they are?  Hopefully somebody does and will let me know.  I must say they have quite a nice pattern to them don't you think?

Mystery seeds?